Apparatus for and method of forming a tubular metal blank into a tapered tube on a tapered mandrel

ABSTRACT

Apparatus for forming a tubular metal blank into a tapered tube on a tapered mandrel, comprising a tapered mandrel and a die assembly through which the tapered mandrel with the tubular metal blank thereon is adapted to be advanced to form the blank into a tapered tube, the die assembly comprising a die having a passage therethrough, the die being composed on non-metallic plastic material capable of being repeatedly deformed from its condition of repose during the forming operation and returned to its condition of repose, a housing in which the die is mounted and means for applying fluid pressure in the housing against the outside of the die to collapse the tubular metal blank about the mandrel as the blank and mandrel pass through the die, the transverse size of the passage in the die when the die is in repose being intermediate, preferably substantially halfway between, the transverse size of the mandrel with the blank collapsed thereabout at the smaller end of the tapered mandrel and the transverse size of the mandrel with the blank collapsed thereabout at the larger end of the tapered mandrel. Also a method of forming a tubular metal blank into a tapered tube on a tapered mandrel, comprising disposing the tubular metal blank about the tapered mandrel, relatively advancing the tapered mandrel with the tubular metal blank thereon and a die as above described so that the tapered mandrel with the tubular metal blank thereon moves through the passage in the die and the die collapses the tubular metal blank about the mandrel, applying fluid pressure to the die when the portion of the mandrel of smallest transverse size is within the passage in the die to contract the die from its condition of repose to collapse the tubular metal blank about that portion of the mandrel and controlling the fluid pressure when the portion of the mandrel of greatest transverse size is within the passage in the die to permit the die to expand from its condition of repose yet effectively collapse the tubular metal blank about that portion of the mandrel. Preferably the fluid pressure applied to the die is controlled so that the die is in its condition of repose when the mid portion of the tapered mandrel with the tubular metal blank thereon is within the passage in the die yet the die effectively collapses the tubular metal blank about that portion of the mandrel. The housing preferably has an opening therethrough constituting a guideway through which the tapered mandrel with the tubular metal blank thereon passes in advancing to the die, the guideway having a transverse size and shape of the tubular metal blank whereby to remove or flatten down outwardly projecting shear fins at the ends of the tubular metal blank to prevent the shear fins from damaging the die. The guideway desirably flares from a transverse size and shape substantially the same as the transverse size and shape of the tubular metal blank adjacent the die to relatively great transverse size more remote from the die.

United States Patent [1 1 Matthews APPARATUS FOR AND METHOD OF FORMING A TUBULAR METAL BLANK INTOA TAPERED TUBE ON A TAPERED MANDREL [75] Inventor: Raymond A. Matthews, Palos Verdes Estates, Calif. [73] Assignee: Reynolds Metals Company,

Richmond, Va.

[22] Filed: Sept. 21, 1971 [21] Appl. No.: 182,403

[52] U.S. Cl. 72/57, 72/276, 72/283,

[51] Int. Cl. B2ld 39/08, B2lc 1/24, B2lc 3/06 [58] Field of Search 72/57, 60, 63, 274,

[56] References Cited UNITED STATES PATENTS 3,570,297 3/1971 Matthews 72/276 3,564,884 2/1971 Hinshaw 2,109,312 2/1938 Dimmick 2,294,138 8/1942 Strock 72/2'74 Primary Examiner-Charles W. Lanham Assistant Examiner-M. J. Keenan Att0mey-Glenn, Palmer, Lyne, Gibbs & Thompson [57] ABSTRACT Apparatus for forming a tubular metal blank into a tapered tube on a tapered mandrel, comprising a tapered mandrel and a die assembly through which the tapered mandrel with the tubular metal blank thereon is adapted to be advanced to form the blank into a tapered tube, the die assembly comprising a die having a passage therethrough, the die being composed on nonmetallic plastic material capable of being repeatedly deformed from its condition of repose during the forming operation and returned to its condition of repose, a housing in which the die is mounted and means for applying fluid pressure in the housing against the out side of the die to collapse the tubular metal blank about June 19, 1973 the mandrel as the blank and mandrel pass through the die, the transverse size of the passage in the diewhen the die is in repose being intermediate, preferably substantially halfway between, the transverse size of the mandrel with the blank collapsed thereabout at the smaller end of the tapered mandrel and the transverse size of the mandrel with the blank collapsed thereabout at the larger end of the tapered mandrel. Also a method of forming a tubular metal blank into a tapered tube on a tapered mandrel, comprising disposing the tubular metal blank about the tapered mandrel, relatively advancing the tapered mandrel with the tubular metal blank thereon and a die as above described so that the tapered mandrel with the tubular :metal blank thereon moves through the passage in the die and the die collapses the tubular metal blank about the mandrel, applying fluid pressure to the die when the portion of the mandrel of smallest transverse size is within the passage in the die to contract the die from its condition of repose to collapse the tubular metal blank about that portion of the mandrel and controlling the fluid pressure when the portion of the mandrel of greatest transverse size is within the passage in the die to permit the die to expand from its condition of repose yet effectively collapse the tubular metal blank about that portion of the mandrel. Preferably the fluid pressure applied to the die is controlled so that the die is in its condition of repose when the mid portion of the tapered mandrel with the tubular metal blank thereon is within the passage in the die yet the die effectively collapses the tubular metal blank about that portion of the mandrel.

The housing preferably has an opening therethrough constituting a guideway through which the tapered mandrel with the tubular metal blank thereon passes in advancing to the die, the guideway having a transverse size and shape of the tubular metal blank whereby to remove or flatten down outwardly projecting shear fins at the ends of the tubular metal blank to prevent the shear fins from damaging the die. The guideway desirably flares from a transverse size and shape substantially the same as the transverse size and shape of the tubular metal blank adjacent the die to relatively great transverse size more remote from the die.

7 Claims, 5 Drawing Figures I I8 I 28 p 4 20 l7 l3 l4 Pmmww V 3.739.616

INVENTOR.

RAYMOND A MATTHEWS BYBQMMI X f jkvmpn HIS ATTORNEYS APPARATUS FOR AND METHOD OF FORMING A TUBULAR METAL BLANK INTO A TAPERED TUBE ON A TAPERED MANDREL This invention is in the nature of an improvement over the invention of my copending US. Pat. application Ser. No. 760,823, filed Sept. 19, 1968, now U.S. Pat. No. 3,570,297.

The invention relates to apparatus for and a method of forming a tubular metal blank into a tapered tube on a tapered mandrel, which is the subject of my said copending application. A die is employed which is composed of a non-metallic plastic material such, for example, as hard and tough nylon, capable of being repeatedly deformed from its condition of repose during the forming operation and returned to its condition of repose, the die being mounted in a housing and means being provided for applying fluid pressure in the housing against the outside of the die to collapse the tubular metal blank about the tapered mandrel as the tubular metal blank and mandrel pass through the die. Reinforced nylons sold as Nylafil and Cadco have been found satisfactory for the die. The die may be mounted in position and the tapered mandrel with the tubular metal blank thereon may be pulled or pushed through the die, or the mandrel and blank may be mounted in position and the die traversed thereon. The forming may be accomplished beginning at either end of the tapered mandrel, i.e., the tapered tube may be formed progressively from its smaller end to its larger end or progressively from its larger end to its smaller end. The mandrel and hence the tapered tube formed thereon may be of circular, polygonal or other cross section. The blank formed into a tapered tube may be of ferrous or non-ferrous metal but must be sufflciently ductile to respond to the forming operation; an example is aluminum.

Apparatus including dies as above described have been used in the formation of tapered metal tubes but problems have arisen which have not in all cases been satisfactorily solved, particularly in the forming of tapered metal tubes of relatively great transverse dimension. When the die in repose, i.e., in a condition in which it is not deformed either by the work passing through the die or by the fluid pressure applied thereto, has the transverse size of the passage therethrough substantially the same as the transverse size of the mandrel with the blank collapsed thereabout at the smaller end of the tapered mandrel, as soon as an adjacent portion of the mandrel of slightly greater transverse size enters the passage in the die the material of the die is immediately placed under tension and the tensile forces to which the material of the die is subjected progressively increase as the tapered mandrel with the blank collapsed thereabout continues to move through the die. When the larger end of the tapered mandrel reaches the die the material of the die is under extreme tensile stress and strain and the die is subject to failure on account of the high tensile stress to which it is subjected. This is especially true in the formation of tapered tubes of relatively large transverse dimension as, for example, tapered tubes tapering from a minimum diameter of 4 inches to a maximum diameter of 8 inches.

l have solved the problem by modification of the size of the die when in repose in relation to the transverse size of the mandrel with the blank collapsed thereabout. I make the transverse size of the passage in the die when the die is in repose intermediate the transverse size of the mandrel with the blank collapsed thereabout at the smaller end of the tapered mandrel and the transverse size of the mandrel with the blank collapsed thereabout at the larger end of the tapered mandrel. Preferably the transverse size of the passage in the die when the die is in repose is substantially half way between the transverse size of the mandrel with the blank collapsed thereabout at the smaller end of the tapered mandrel and the transverse size of the mandrel with the blank collapsed thereabout at the larger end of the tapered mandrel. I provide for applying fluid pressure to the die when the portion of the mandrel of smallest transverse size is within the passage in the die to contract the die from its condition of repose to collapse the tubular metal blank about that portion of the mandrel and controlling the fluid pressure when the portion of the mandrel of greatest transverse size is within the passage in the die to permit the die to expand from its condition of repose yet effectively collapse the tubular metal blank about that portion of the mandrel. Desirably the fluid pressure applied to the die is controlled so that the die is in its condition of repose when the mid portion of the tapered mandrel with the tubular metal blank thereon is within the passage in the die yet the die effectively collapses the tubular metal blank about that portion of the mandrel.

An example of my invention is the utilization of a die having a passage 6 inches in diameter when the die is in repose to form a tapered tube whose smallest diameter is 4 inches and whose greatest diameter is 8 inches. When the smaller end of the work, i.e., the tapered mandrel with the tubular blank thereabout, is within the passage in the die the die is contracted about the work by the fluid pressure applied to the die so that the material of the die in contact with the work is under compression rather than under tension. Compressive stress is less detrimental to the material of the die than tensile stress. Moreover, as the operation progresses and the portion of the mandrel of increasing transverse dimension passes through the die the compressive stress decreases until at the mid portion of the length of the work the die is virtually in a state of repose with the material of the die in engagement with the work free from either high compressive stress or high tensile stress. As the operation continues the material of the die in contact with the work is subjected to progressively increasing tensile stress, but the tensile stress at the end of the operation is much less than when a die is used which in its condition of repose has its passage of substantially the same transverse dimension as the smaller end of the work. The result is diminution of die failure and the ability to use material for the die which has a reduced ultimate strength. Stated otherwise, a die of given material can be used to form a tapered tube of increased transverse dimension when my invention is utilized.

The tubular metal blank may be formed by sawing it out of a longer tube, which leaves outwardly projecting shear fins at the ends of the tubular metal blank which damage the die if they are forced into contact with the die. To remove or flatten down the shear fins I provide the housing with an opening therethrough constituting a guideway through which the tapered mandrel with the tubular metal blank thereon passes in advancing to the die, the guideway having a transverse size and shape substantially the same as the transverse size and shape of the tubular metal blank. Thus when the tubular metal blank passes through the guideway the shear fins are removed or at least minimized so that they do not damage the die. The guideway preferably flares from a transverse size and shape substantially the same as the transverse size and shape of the tubular metal blank adjacent the die to relatively great transverse size more remote from the die to facilitate guiding the tubular metal blank to the die.

Other details, objects and advantages of the invention will become apparent as the following description of a present preferred embodiment thereof and a present preferred method of practicing the same proceeds.

In the accompanying drawings I have shown a present preferred embodiment of the invention and have illustrated a present preferred method of practicing the same in which FIG. 1 is a fragmentary side elevational view with portions shown in central vertical cross section of a tube-drawing apparatus including a die assembly embodying the novel features of the present invention;

FIG. 2 is a fragmentary side elevational view generally similar to part of FIG. 1 showing the entire length of the tube to be drawn and partly broken away and shown in cross section;

FIG. 3 is an enlarged detail cross-sectional view of the die assembly near the beginning of the drawing of a tubular metal blank into a tapered tube on a tapered mandrel, the tapered tube being formed beginning at the smaller end;

FIG. 4 is a view similar to FIG. 3 at the mid point of the drawing of the tapered tube on the tapered mandrel; and

FIG. 5 is a view similar to FIGS. 3 and 4 at the end of the drawing of the tapered tube on the tapered mandrel.

As shown in FIGS. 1 and 2, for purposes of illustration the invention is embodied in a die assembly mounted on a post 11 upstanding from a conventional horizontal draw bench 12 with a section 13 of tubing constituting a tubular metal blank telescoped onto a tapered mandrel 14 ready to be drawn. In the usual fashion, one end portion 15 of the tubular metal blank is pointed" to reduced diameter so as to extend loosely through a die 17 in the die assembly and into a horizontal bore 18 in the post, where it is gripped in a chuck 19 on the end of a rod 20 connected at 21 to the reciprocating piston rod 22 of a horizontal hydraulic cylinder 23.

The cylinder 23 is pivotally anchored at 24 on the left-hand portion of the bench 12 so that admission of fluid under pressure to the right-hand end of the cylinder through a supply line 25 shifts the piston rod 22 to the left to draw the chuck 19 to the left and pull the tube 13 through the die 17. A second fluid line 27 is connected to the left-hand end of the cylinder to effect the return stroke of the piston rod. It should be understood that this draw bench arrangement is merely representative of various types of conventional benches that are well known in the art, and that the construction of the bench is not part of the present invention.

During the forward stroke of the piston rod 22, to the left as viewed in the drawings, the tube 13 and mandrel 14 are pulled together through the die assembly 10, which herein is held stationary in a recess 28 in the right-hand side of the post 11. Thus the tubular metal blank is sized and shaped by the die 17 around the mandrel inside the tubular metal blank.

The die 17 is composed of relatively hard and tough, non-metallic plastic material capable of expanding and contracting repeatedly in annular form within a substantial range without rupturing or hardening. Stated somewhat differently, the die is capable of being repeatedly deformed from its condition of repose during the forming operation and returned to its condition of repose. The die 17 is of the form shown in my said copending application, being of generally spool shape mounted in a housing 16. A compressive force of fluid under pressure is uniformly distributed in a groove chamber 33 in the die. The die is rigidly supported within the housing 16 of the die assembly 10 against axial yielding under the drawing force exerted by the cylinder 23. Fluid under pressure controlled by a pressure relief valve 44 is admitted to the die through a connection 32 and enters the groove chamber 33 to insure proper action of the die in forming or crushing the tubular metal blank 13 about the tapered mandrel 14.

I make the die 17 such that the transverse size of the central passage in the die when the die is in repose is intermediate the transverse size of the mandrel with the blank collapsed thereabout at the smaller end of the tapered mandrel and the transverse size of the mandrel with the blank collapsed thereabout at the larger end of the tapered mandrel, and I find it desirable for optimum results to make the transverse size of the passage in the die when the die is in repose substantially halfway between the transverse size of the mandrel with the blank collapsed thereabout at the smaller end of the tapered mandrel and the transverse size of the mandrel with the blank collapsed thereabout at the larger end of the tapered mandrel. The die is shown in a condition of repose in FIG. 4 at which time the mid point of the tapered tube being formed is in the die. FIG. 3 shows the beginning of the forming operation and FIG. 5 shows the end thereof. By way of example, the opening in the die in repose may have a diameter of 6 inches in FIG. 4 and may be compressed by fluid pressure to a diameter of 4 inches in FIG. 3 and may be stretched by the mandrel and blank with suitable fluid pressure control to a diameter of 8 inches in FIG. 5. The result of such design of the die is, as explained above, that the die is subjected to much less tensile stress than when the die in repose has its passage of the same transverse size as that of the mandrel with the blank collapsed thereabout at the smaller end of the tapered mandrel. The compressive stress to which the die is subjected at the beginning of the operation is not detrimental and the maximum tensile stress to which the die is subjected at the end of the operation is greatly reduced whereby the advantages above pointed out are realized.

The entrance side of the die assembly housing 16 designated 34 has an opening 35 therethrough constituting a guideway through which the tapered mandrel 14 with the tubular metal blank 13 thereon passes in advancing to the die. The guideway has a transverse size and shape substantially the same as the transverse size and shape of the tubular metal blank whereby to remove or flatten down outwardly projecting shear fins at the ends of the tubular metal blank to prevent the shear flns from damaging the die. The guideway preferably flares from a transverse size and shape substantially the same as the transverse size and shape of the tubular metal blank 13 adjacent the die at 36 to relatively great transverse size more remote from the die at 37. Thus the opening 35 serves both to assist in guiding the work to the die and also to eliminate the outwardly projecting shear fins from the tubular metal blank which if not eliminated would damage the die.

While I have shown and described a present preferred embodiment of the invention and have illustrated a present preferred method of practicing the same, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.

l claim:

1. Apparatus for forming a tubular metal blank into a tapered tube on a tapered mandrel, comprising a tapered mandrel and a die assembly through which the tapered mandrel with the tubular metal blank thereon is adapted to be advanced to form the blank into a tapered tube, the die assembly comprising a die having a passage therethrough, the die being composed of nonmetallic plastic material capable of being repeatedly deformed from its condition of repose during the forming operation and returned to its condition of repose, a housing in which the die is mounted and means for applying fluid pressure in the housing against the outside of the die to collapse the tubular metal blank about the mandrel as the blank and mandrel pass through the die, the transverse size of the passage in the die when the die is in repose being intermediate the transverse size of the mandrel with the blank collapsed thereabout at the smaller end of the tapered mandrel and the transverse size of the mandrel with the blank collapsed thereabout at the larger end of the tapered mandrel.

2. Apparatus for forming a tubular metal blank into a tapered tube on a tapered mandrel as claimed in claim 1 in which the transverse size of the passage in the die when the die is in repose is substantially halfway between the transverse size of the mandrel with the blank collapsed thereabout at the smaller end of the tapered mandrel and the transverse size of the mandrel with the blank collapsed thereabout at the larger end of the tapered mandrel.

3. A method of forming a tubular metal blank into a tapered tube on a tapered mandrel, comprising disposing the tubular metal blank about the tapered mandrel, relatively advancing the tapered mandrel with the tubular metal blank thereon and a die having a passage therethrough and composed of non-metallic plastic material capable of being repeatedly deformed from its condition of repose and returned to such condition so that the tapered mandrel with the tubular metal blank thereon moves through the passage in the die and the die collapses the tubular metal blank about the man drel, applying fluid pressure to the die when the portion of the mandrel of smallest transverse size is within the passage in the die to contract the diefrom its condition of repose to collapse the tubular metal blank about that portion of the mandrel and controlling the fluid pressure when the portion of the mandrel of greatest trans verse size is within the passage in the die to permit the die to expand from its condition of repose yet effectively collapse the tubular metal blank about that portion of the mandrel.

4. A method of forming a tubular metal blank into a tapered tube on a tapered mandrel as claimed in claim 3 in which the fluid pressure applied to the die is controlled so that the die is in its condition of repose when the mid portion of the tapered mandrel with the tubular metal blank thereon is within the passage in the die yet the die effectively collapses the tubular metal blank about that portion of the mandrel.

5. Apparatus for forming a tubular metal blank into a tapered tube on a tapered mandrel, comprising a tapered mandrel and a die assembly through which the tapered mandrel with the tubular metal blank thereon is adapted to be advanced to form the blank into a tapered tube, the die assembly comprising a die having a passage therethrough, the die being composed of nonmetallic plastic material capable of being repeatedly deformed from its condition of repose during the forming operation and returned to its condition of repose, a housing in which the die is mounted and means for applying fluid pressure in the housing against the outside of the die to collapse the tubular metal blank about the mandrel as the blank and mandlrel pass through the die, the housing having an opening therethrough constituting a guideway through which the tapered mandrel with the tubular metal blank thereon passes in ad vancing to the die, the guideway having a transverse size and shape substantially the same as the transverse size and shape of the tubular metal blank whereby to remove or flatten down outwardly projecting shear fins at the ends of the tubular metal blank to prevent the shear fins from damaging the die.

6. Apparatus for forming a tubular metal blank into a tapered tube on a tapered mandrel as claimed in claim 5 in which the guideway flares from a transverse size and shape substantially the same as the transverse size and shape of the tubular metal blank adjacent the die to relatively great transverse size more remote from the die.

7. Apparatus for forming a tubular metal blank into a tapered tube on a tapered mandrel as claimed in claim 1 in which the housing has an opening therethrough constituting a guideway through which the tapered mandrel with the tubular metal blank thereon passes in advancing to the die, the guideway having a transverse size and shape substantially the same as the transverse size and shape of the tubular metal blank whereby to remove or flatten down outwardly projecting shear fins at the ends of the tubular metal blank to prevent the shear fins from damaging the die. 

1. Apparatus for forming a tubular metal blank into a tapered tube on a tapered mandrel, comprising a tapered mandrel and a die assembly through which the tapered mandrel with the tubular metal blank thereon is adapted to be advanced to form the blank into a tapered tube, the die assembly comprising a die having a passage therethrough, the die being composed of non-metallic plastic material capable of being repeatedly deformed from its condition of repose during the forming operation and returned to its condition of repose, a housing in which the die is mounted and means for applying fluid pressure in the housing against the outside of the die to collapse the tubular metal blank about the mandrel as the blank and mandrel pass through the die, the transverse size of the passage in the die when the die is in repose being intermediate the transverse size of the mandrel with the blank collapsed thereabout at the smaller end of the tapered mandrel and the transverse size of the mandrel with the blank collapsed thereabout at the larger end of the tapered mandrel.
 2. Apparatus for forming a tubular metal blank into a tapered tube on a tapered mandrel as claimed in claim 1 in which the transverse size of the passage in the die when the die is in repose is substantially halfway between the transverse size of the mandrel with the blank collapsed thereabout at the smaller end of the tapered mandrel and the transverse size of the mandrel with the blank collapsed thereabout at the larger end of the tapered mandrel.
 3. A method of forming a tubular metal blank into a tapered tube on a tapered mandrel, comprising disposing the tubular metal blank about the tapered mandrel, relatively advancing the tapered mandrel with the tubular metal blank thereon and a die having a passagE therethrough and composed of non-metallic plastic material capable of being repeatedly deformed from its condition of repose and returned to such condition so that the tapered mandrel with the tubular metal blank thereon moves through the passage in the die and the die collapses the tubular metal blank about the mandrel, applying fluid pressure to the die when the portion of the mandrel of smallest transverse size is within the passage in the die to contract the die from its condition of repose to collapse the tubular metal blank about that portion of the mandrel and controlling the fluid pressure when the portion of the mandrel of greatest transverse size is within the passage in the die to permit the die to expand from its condition of repose yet effectively collapse the tubular metal blank about that portion of the mandrel.
 4. A method of forming a tubular metal blank into a tapered tube on a tapered mandrel as claimed in claim 3 in which the fluid pressure applied to the die is controlled so that the die is in its condition of repose when the mid portion of the tapered mandrel with the tubular metal blank thereon is within the passage in the die yet the die effectively collapses the tubular metal blank about that portion of the mandrel.
 5. Apparatus for forming a tubular metal blank into a tapered tube on a tapered mandrel, comprising a tapered mandrel and a die assembly through which the tapered mandrel with the tubular metal blank thereon is adapted to be advanced to form the blank into a tapered tube, the die assembly comprising a die having a passage therethrough, the die being composed of non-metallic plastic material capable of being repeatedly deformed from its condition of repose during the forming operation and returned to its condition of repose, a housing in which the die is mounted and means for applying fluid pressure in the housing against the outside of the die to collapse the tubular metal blank about the mandrel as the blank and mandrel pass through the die, the housing having an opening therethrough constituting a guideway through which the tapered mandrel with the tubular metal blank thereon passes in advancing to the die, the guideway having a transverse size and shape substantially the same as the transverse size and shape of the tubular metal blank whereby to remove or flatten down outwardly projecting shear fins at the ends of the tubular metal blank to prevent the shear fins from damaging the die.
 6. Apparatus for forming a tubular metal blank into a tapered tube on a tapered mandrel as claimed in claim 5 in which the guideway flares from a transverse size and shape substantially the same as the transverse size and shape of the tubular metal blank adjacent the die to relatively great transverse size more remote from the die.
 7. Apparatus for forming a tubular metal blank into a tapered tube on a tapered mandrel as claimed in claim 1 in which the housing has an opening therethrough constituting a guideway through which the tapered mandrel with the tubular metal blank thereon passes in advancing to the die, the guideway having a transverse size and shape substantially the same as the transverse size and shape of the tubular metal blank whereby to remove or flatten down outwardly projecting shear fins at the ends of the tubular metal blank to prevent the shear fins from damaging the die. 